1. Field of the Invention
The present invention relates to an improvement in a center hub cap to be mounted on a vehicle wheel for covering a wheel center hole.
2. Description of the Related Art
There is shown, in FIGS. 14 and 15, a typical example of the center hub cap as mentioned above, which includes a generally disc-like main body 1 composed of a flexible material, such as a thermoplastic synthetic resin. The main body 1 has a plurality of integral hook-like projections 2 arranged on its rear surface so as to project therefrom axially rearwardly. The projections 2 can be resiliently deflected radially inwardly as they are inserted into a center hole in a vehicle wheel to mount the cap thereon. Furthermore, each projection 2 has a free end in the form of a stepped portion 3 which is engageable with the periphery of the center hole on its rear side, so that the cap can be mounted on and retained by the wheel and the wheel center hole is covered by the cap.
In the above-mentioned known arrangement of the center hub cap, the projections 2 extending from the main body 1 should have a substantial length in order to ensure that they can be sufficiently deflected radially inwardly when mounting the cap on the wheel. Thus, such a cap can be used only in combination with a wheel whose center hole is to be located remote from the main body 1 of the cap. In other words, for a wheel having a center hole which is to be located close to the main body 1 of the cap or which is of a small depth, the length of each projection 2 has to be decreased to locate the stepped portion 3 close to the main body 1 of the cap. Then it becomes relatively difficult to achieve a sufficient deflection of the projections 2, and even a small dimensional deviation of the cap itself, or of the wheel center hole, results in that the cap cannot be stably retained by the wheel, and frequency gives rise a tendency of undesirable and often dangerous separation of the cap from the wheel. Moreover, the projections 2 tend to get damaged prematurely since their root end portions in connection with the main body 1 are subjected to a severe bending moment due to the insufficient length or flexibility thereof.
In this context, Japanese Patent Application Publication No. 52-39,531 discloses a vehicle wheel cover which includes a plurality of spring clips mounted on the rear side of the cover to be resiliently engaged with the rim of a wheel. These clips might be incorporated into a center hub cap to thereby permit the cap to be used also in combination with a wheel having a center hole which is of a small depth, or is to be located close to the main body. Nevertheless, use of such clips is disadvantageous as requiring additional and troublesome assembly steps of separate components, and also as resulting in a structural complexity as well as an increased production cost.